How to modify select identifiers

I want to modify select identifiers in sql statement. For example
SELECT value FROM Data
to
SELECT value as v FROM Data
I am able to get SqlNode for select identifiers as follows.
public String visit(SqlCall sqlCall) {
SqlNodeList selectList = ((SqlSelect) sqlCall).getSelectList();
for (SqlNode sqlNode : selectList) {
*// do something with sqlNode*
}
}
Now how to change sqlNode as per requirement?
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Regards
Shashwat Kumar